I was replacing my PCV valve and gromet and in the mean time I broke a dryrotted vaccum hose that runs into the back of the manifold...Now i noticed my car is idling higher...My question is: Is this something i need to fix or worry about?
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91 LX...Motor is out and waiting for 347 to be finished for next season..All bolt-ons with Nitrous...100% dragster...
Do you mind explaining this "lean" condition to me please?..Ty
BTW..it was not the actual hose that runs to the PCV vale...I guess the MOd changed the subject title...It is the hose above it running into the back of the manifold..the other end goes into a group of wires then into the firewall.
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91 LX...Motor is out and waiting for 347 to be finished for next season..All bolt-ons with Nitrous...100% dragster...
optimum fuel mixture is called, stoch i think, if i'm not mistaken, lean is when it has more air than fuel (porportional to the proper mixture, rich is when there is too much fuel, vacuume leaks cause it to be too lean because it adds more air in,
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89 fox, mostly stock, C&L 73mm MAF, bypassed coolant hoses to egr spacer, intake silencer removal, no a/c, all options but power mirrors?? blown cats, msd cap and rotor, bosch wires, autolite plugs, 5 inch auto gauge tach with recal and blue lensed shift light, PAPER FILTER I BOUGHT ONE!!!!!!! felpro gasgets on everywhere accept oil pan and a nice big classic mustang decal on my back window
A lean condition means that your air fuel mixture is no correct.There is to much air.The extra air is getting in from your vacuum leak.A lean condition usually will cause the engine to rev higher at idle.
[quote=pro5o]A lean condition means that your air fuel mixture is no correct.There is to much air.The extra air is getting in from your vacuum leak.A lean condition usually will cause the engine to rev higher at idle.[/QUOTE
I dont know, but doesn't running rich raise idle too?
Idle in our Mustangs are controlled by controlling a vacuum leak from the outside of the accelerator blade into the upper intake, this is why the idle jumps anytime you have a vacuum leak anywhere else. The reason for the A/F to get "leaned out" when you have a vacuum leak, is that it is air getting into the intake that has not been "metered" by the MAF (it's not part of the input used to calibrate A/F by the system).
Having that "unmetered" air in the intake causes the system to try to set A/F(injectors pulse-width) based on what the MAF registered, since you have more air than the one measured...it gets a lean result. The vacuum leak used to control idle by the IAC, uses air that was measured by the MAF already, so it's part of the equation for A/F setting.
You get higher idle when running rich b/c the system is preventing a stall + if it's close to the limits trying to lean out the A/F, it will start changing parameters, idle included, to get the A/F to ideal stoichiometry (14.64 for the EEC-IV). Hope this helps.
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LUK=Let Us Know, GL=Good Luck, LMK=Let Me Know, JIC=Just In Case, BTSTDTRT=Been There Seen That Done That Repaired That, YCYDYP=Your Car Your Dough Your Prerogative and the classic... DILLIGAS=Do I Look Like I Give A S***
1986 GT-X303 cam, 289 heads, 1.72, Holley 700cfm DP, RG 4+1 Trans.
Vacuum hose to pcv broke and idle is higher? 
, msd cap and rotor, bosch wires, autolite plugs, 5 inch auto gauge tach with recal and blue lensed shift light, PAPER FILTER 
